Solar power plant/equipment utilizing solar light has become widely used along with diversification of energy resources. Although small-scale power equipment on a scale of installation on roofs of houses has been drawing attention from the beginning, construction of large-scale solar power plants (so-called mega solar power plants) exceeding 1000 KW is thriving due to the lack of energy sources in recent years or from the viewpoint of controlling emissions of CO2. Hereinafter, an installation location of a photovoltaic power plant will also be called a “power plant site”, a location of the power plant site will also be called a “field”, a unit solar power panel will also be called a “solar module”, an elongated panel with several or more than ten modules integrated in series will also be called a “solar string”, and a parallel array of a large number of “solar strings” will also be called a “solar array”, expediently.
In the construction of this type of solar power plant, a plurality of solar modules are integrated by parallel beams or frame-shaped module support frames to form solar strings, and the solar strings are arranged in an array on stands provided in a power plant site. The assembly and the installation work of the solar strings are generally performed in the power plant site (for example, Patent Document 1). A method is also known, in which the solar strings are assembled in a plant, and the solar strings are housed in a container and transported to the power plant site (Patent Document 2).